1. Field of the Invention
This invention relates to metallurgical furnaces of the type used to reheat metal prior to hot working, wherein certain water-cooled furnace members are covered with refractory material so as to insulate and protect them from the hot furnace gases.
2. Description of Related Art
Furnaces for heating metal during processing often operate at temperatures up to about 2400.degree. F. At such elevated temperatures it is necessary to protect furnace structural members from such intense heat. Furnace members providing support for heavy metal sections, such as billets or slabs being heated in such furnaces, are insulated and cooled internally with circulating fluid so as to maintain the strength required to support such loads.
Furnace support members for heavy metal sections, commonly referred to as skid rails, typically consist of horizontally oriented water cooled pipes having an upwardly projecting wear surface along their length. The heavy metal sections to be heated are slid along the wear surfaces of such support members as they move from the furnace entrance to the furnace exit. Insulation for the support members is commonly of a single refractory material or can be made up of layered composite materials. A multitude of different means are employed to secure the insulation to the furnace members in a manner to withstand the high temperature, thermal shock, vibration, and other forces to which the furnace members and insulation are subjected. Relative ease of installation is of importance due to the requirement for periodic replacements.
U.S. Pat. No. 3,881,864 describes a refractory tile surrounding an inner fibrous refractory material about a furnace skid rail wherein two complimentary c-shaped blocks inter-engage beneath the skid rail to secure the insulation in place. No additional means is provided for securement.
U.S. Pat. No. 4,393,569 describes a module wherein the support member is wrapped with refractory fiber insulating material which is protected by an outer refractory ceramic fiber blanket folded into at least two layers.
U.S. Pat. No. 4,140,484 describes a tubular supporting member sheathed by refractory sheathing comprising an inner layer of fibrous refractory material and an outer layer of refractory tiles held in place by metal links which are secured together around the supporting members.
U.S. Pat. No. 4,071,311 describes a metal tubular supporting member sheathed by an inner layer of refractory fibrous material and an outer layer consisting of pairs of semi-cylindrical refractory tiles. The refractory tiles are held in place by metal coupling links covered and positively engaged by adjacent tiles.
U.S. Pat. No. 4,015,636 describes a three-layer insulating assembly comprising an inner fibrous thermal insulation, an intermediate split ceramic refractory, and an outer protective ceramic covering.
U.S. Pat. No. 4,450,872 describes a covering comprising an inner layer of thermal insulating ceramic refractory fiber blanket, an open weave ceramic cloth about the blanket, an inner layer of veneering mortar, compressed rings of ceramic fiber material, and a hot face layer of veneering coating.
U.S. Pat. No. 3,881,864 describes a refractory tile for sheathing a furnace member, preferably around an inner layer of fibrous refractory material. "C" shaped complimentary tiles interengage each other underneath the member to hold them in position.
All of the listed prior art insulating tiles incorporate at least two layers of insulating material with each layer having generally concentric inner and outer cylindrically shaped surfaces.